The concept of a biological species refers to a group of organisms that can interbreed and produce fertile offspring. This means that members of the same species share similar characteristics and genetic makeup, allowing them to reproduce successfully. For example, dogs and cats are different species because they cannot produce offspring together. In addition to reproduction, biological species are often defined by their ability to adapt to similar environments and ecological niches. This helps maintain the distinctiveness of each species. For instance, lions and tigers are both part of the larger family of big cats, but they are separate species due to their unique traits and behaviors.